Post hoc ergo propter hoc

When a cause of a phenomenon is attributed to a prior phenomenon without providing sufficient evidence of a causal link.

After I started wearing a copper bracelet, my health improved! It worked!

Also known as: false cause / coincidental correlation

Notes

Causation must be rigorously demonstrated. Phenomena that occur in sequence do not necessarily have a causal link. This fallacy is related to the correlation is not causation fallacy.

Case Study One

Most people feel a period of elation every time they voluntarily change jobs. Many are tempted to cite the conditions of the new job as the reason for their better mood. Is it the new job that is causing the elation, or merely the change?

Case Study Two

Because a common cold runs its normal course after a few days, any medicine taken during that time may be erroniously proclaimed effective.

Case Study Three

The occasional occurance of a desired outcome after the prayer for that outcome by a religious person is often offered as “evidence” for the efficacy of prayer. Yet the times that there was a prayer with an undesirable outcome is not admitted as counter-evidence, and the similarly “answered” prayers made to gods of other religions are dismissed as coincidents.